1. Field of the Invention
The present invention relates to a curable composition suitable for producing a color filter to be used for a liquid crystal display element (LCD), a solid image pickup element (such as CCD and CMOS), or the like, a color filter formed with the curable composition, and a manufacturing method therefor.
2. Description of the Related Art
The color filter is an essential constituent part for a liquid crystal display or a solid image pickup element.
Since the liquid crystal display is compact and having the equivalent or superior performance compared with the CRT commonly used as a display apparatus, it is replacing the CRT as the television screen, the personal computer screen, and the other display apparatus. Moreover, recently, as to the trend of the development of the liquid crystal display, it is changing from the conventional monitor application having a screen of a relatively small area to the television application having a large screen and a higher image quality. As to the color filter for the liquid crystal display (LCD), the substrate size is made larger for the production of the large scale television sets. The curable composition for the application of the color filter production using such a large substrate, curability with low energy is required for the improvement of the productivity.
Moreover, compared with those for the monitor application, a higher image quality is required to the liquid crystal display for the television application, that is, improvement of the contrast and the color purity.
For the curable composition for the application of the color filter production, for the purpose of improvement of the contrast, a coloring agent (organic pigment, or the like) to be used of a finer particle size is required (see for example, Japanese Patent Application Laid Open (JP-A) No. 2006-30541).
However, if the pigment absorbing property of the dispersing agent is improved for the purpose of improvement of the dispersion stability at the time of containing a pigment with a small particle size in the curable composition, due to cross-linking in the pigment by the dispersing agent, the pigment aggregation is promoted so that the storage stability such as the dispersion stability is lowered or the developability at the time of forming a pattern using the curable composition tends to be lowered.
Moreover, in the case of using a finer pigment, since the surface area thereof is increased, use of the finer pigment tends to increase the addition amount of the dispersing agent for dispersing the pigment in the curable composition.
Furthermore, if the acid value of the resin to be added at the time of dispersion is improved for ensuring the developability, aggregation of the pigment tends to be promoted by the interaction between the acidic groups such as the hydrogen bond.
If the developability is to be obtained by adding a resin to the curable composition after dispersing the pigment, a large amount of the resin should be added. Moreover, for the purpose of the improvement of the color purity, a higher content ratio of the coloring agent (organic pigment) in the solid component is required in the curable composition used for producing a color filter. However, when the coloring agent is contained in the curable composition at a high concentration, the content ratio of the photopolymerization initiator and the photo polymerizable monomer in the curable composition is reduced, and although the curable composition therefore needs to be curable at low energy, the difficulty of achieving curability in an exposed portion is problematic. On the other hand, as to the curable composition for the application of the production of the color filter for the solid image pickup element, curability with a low energy is called for. Moreover, as to the color filter for the application of the solid image pickup element, development of a thinner film of the colored pattern is promoted, and accompanied thereby, increasing the pigment concentration in the composition.
Furthermore, in the pigment based color filter, accompanied by the trend toward a finer pigment for reducing the color irregularity derived from the fact that the pigment is a relatively coarse particle, the content ratio of the pigment dispersing agent in the curable composition tends to be increased. Similar to the case of the curable composition for the purpose of the production of the LCD, the increase of the content ratio of the pigment dispersing agent in the curable composition tends to lower the storage stability such as the dispersion stability, tends to lower the developability at the time of forming a pattern using the curable composition, and hardly obtains the curability, and thus it is problematic.
Moreover, for coping with the problems such as the color irregularity in the formed colored pattern, a technique of using an organic solvent soluble dye as the coloring agent instead of the pigment has been proposed (see for example, JP-A No. 2-127602). However, as to the dye based color filter, accompanied by the increase of the dye concentration, problems of the storage stability decline such as the polymerization inhibiting effect derived from the dye, and precipitation of the dye have been remarkable.
As mentioned above, according to the curable composition for the application of the color filter production, either in the case of those for the liquid crystal display or in the case of those for the solid image pickup element, since the content amount of the photopolymerization initiator and the photo polymerizable monomer as the essential component for curing the curable composition is limited and furthermore, the coloring agent concentration is high, various problems arises in that the sufficient curability is not obtained due to the low sensitivity, the adhesion to the substrate is insufficient, the developing rate is lowered or the residue is generated in the unexposed part, a desired pattern may be formed extremely hardly, the dispersion stability and the developability are poor in the case the coloring agent is a pigment, the storage stability is low such as the precipitation of the dye in the case the coloring agent is a dye, or the like.
In order to cope with these problems, improvement of the sensitivity has been discussed by providing the polymerizable property to a resin introduced conventionally for providing mainly the film forming property, the developability, or the like (see for example, JP-A Nos. 2000-321763 and 2003-029018). Additionally, the technique is presented in columns 85 to 87 of “Color Filter Latest Technique Trend” (published by Johokiko Co., Ltd.), columns 129 to 150 of “Process Technique and Chemicals for Latest Color Filter” (published by CMC Publishing Co., Ltd.), or the like. However, even in the case of using these resins, satisfactory exposure sensitivity has not been obtained so far. Furthermore, due to the insufficient exposure sensitivity, curing is insufficient in the deep portions in the vicinity of the substrate interface, or the like so that a problem of the poor substrate adhesion property, or the like has also been involved.
An object of the invention is to provide a curable composition to be cured with an extremely high sensitivity, having preferable storage stability.
Moreover, another object of the invention is to provide a color filter formed using the above-mentioned curable composition, having a high sensitivity, little development residue in the uncured portion, the excellent adhesion property of the cured portion with respect to the substrate, and a colored pattern with a high resolution and a desired cross-sectional shape.
Furthermore, still another object of the invention is to provide a manufacturing method for the above-mentioned color filter with the excellent productivity, and a solid image pickup element having the above-mentioned color filter manufactured by the manufacturing method.
According to their elaborate study in view of the above-mentioned circumstances, the inventors have been found out that the above-mentioned problems may be solved so as to complete the invention.